Project 3 - Violet's Vending Venture

Introduction

Your friend Violet and her family are considering starting a vending machine business. To make sure it will be profitable, they have decided to keep it simple and plan! The planning part is where you get involved. She wants you to create a program that will allow her to simulate some of the possibilities of their business decisions. The goal is to have a program that represents the different kinds of vending machines they currently intend to operate with the possibility of adding different machine types in the future. The program will simulate the machines and model the profit of each machine and the whole business (the sum of the profit of all the machines). You both realize that this means a program that uses inheritance to represent different kinds of vending machines which will make the code simpler, more flexible, and easier to maintain.

Together you decide that you will largely model profit. First to consider is the individual machine profit so that you can tell if individual machine locations are profitable. Second is the total profit of the whole business. Violet also decides that she wants to model a basic machine with only one kind of product that doesn't require anything special to operate first. But, she will consider two other kinds of machines that have a bit more sophistication in their functionality. Specifically she will want to add a drink machine, where the whole machine is still filled with the same product, but now each product will have an added cost charged to it for the refrigeration. Both the basic machine and the drink machine will require exact change. The last machine she wants to model is a traditional snack machine. It requires no refrigeration, but each slot in the machine will be loaded with a different snack product which could have a different cost, and it will return change when something is bought. In support of this vision, you have come up with the UML diagram below.

Submission and Honor Code

Submissions should be made by the due dates listed on Canvas. There are no late submissions unless specified by your instructor otherwise. The Gradescope results will reflect the no late submissions policy. Only the latest submission to Gradescope will be graded and code that does not compile will receive a 0, so please be careful with last minute submissions. Your final grade will be determined largely by correctness as determined by your Gradescope score, but documentation, and overall code quality will also be considered.

Though you are encouraged to discuss concepts with peers, teaching assistants and the instructor, the source code you submit should be your own work and something you could replicate on your own. Representing someone (or something) else's work as your own, in any form, constitutes an honor code violation. Directly copying or using the same code is an honor code violation. It is also a violation of the honor code to "render unauthorized assistance to another student by knowingly permitting him or her to copy all or a portion of an examination or any work to be submitted for academic credit." That means that you can be written up for an Honor code violation if you share your code with someone else, even if you wrote it completely on your own. If you violate the University Honor Code, you will receive a reduced or failing grade for the assignment or other penalties may be imposed and the violation will be reported to the Honor Council.

Individual instructors may have additional requirements. Please consult the syllabus for your section for details.

Learning Outcomes

• Implement a UML diagram that uses inheritance.
• Correctly implement examples of overriding and overloading.
• Correctly predict via simulation the interaction of objects from an inheritance hierarchy.
• Implement a program that makes use of ArrayLists.

UML Diagram

The connectors in the UML diagram below now include inheritance. Recall, this tutorial: UML Tutorial

Implement the class and methods according to the UML and specifications below.

Part 1 - Create Product.java and ProductTest.java

The Product class models an individual item type in a vending machine. Each product has a name, cost. and price. Note that cost is the cost of the product to the vending machine company. Price is the price that the vending machine will charge the customer. Violet has said that she is unwilling to deal with anything but quarters, dollar bills, and debit cards so all prices are kept divisible by 25 cents. Costs to the vending machine company can be any penny value. All of the get methods perform the expected operation.

Data

Note: cost and price are both integers. All money in the vending machine is represented as cents to enable simpler math and eliminate rounding issues.

• ROUND_PRICE: int - the value in cents to which all prices will be rounded
• name: String - the name of the product type
• cost: int
• price: int

Product()

The default constructor will create an instance of a product with a name of "Generic", a cost of ROUND_PRICE = 25 cents and a price of twice the ROUND_PRICE.

Product(String name, int cost, int price) throws IllegalArgumentException

This constructor takes the name, cost, and price as parameters and sets the instance variables appropriately. Null string names or negative cost or price should throw an IllegalArgumentException. Prices should be rounded to the next ROUND_PRICE cents above the amount given if the amount given if not already divisible by ROUND_PRICE. Note: if the price given is not greater than the cost, the price should be the next ROUND_PRICE-divisible-value that is greater than the cost.

toString()

The toString() method will return a String of the instance variables of the class exactly as shown below. Assuming a name of "M&Ms", cost of $1.02, and a price of $1.25, toString() would return:

Product: M&Ms Cost: 1.02 Price: 1.25.

Note: the cost and price are kept in cents so the toString() method will need to transform the values into the right format.

Part 2 - Create Slot.java and SlotTest.java

The Slot class models a slot in the vending machine. Slots are loaded from the rear, and purchases are removed from the front. This ensures that the items that have been in the machine the longest are sold before newly added items.

Data

• SLOT_SIZE: int = 10 - the maximum number of products that a slot in the vending machine can hold.
• products: ArrayList<Product> - models the actual products that are in the slot. Removing the one at the front models buying one of the products in the slot and all of the others are moved forward similar to an actual vending machine.

Slot()

The Slot() constructor creates an empty array list of products.

Slot(Product product)

This constructor creates a new slot that is filled with SLOT_SIZE of product.

load(Product product)

This method loads the slot with however many new products are required to make sure it is full and returns the number of products it took to fill the slot.

load(Product product, int count)

This method loads the slot with up to count new products in an attempt to fill the slot and returns the number of products it used.

nextProduct()

This method returns a reference to the next product available for purchase. If the slot is empty this method will return null.

buyOne()

This method simulates the purchase of one item from the perspective of the slot. That means no money is dealt with here, rather the slot is checked to make sure there is product to buy and then one product is removed from the front of the ArrayList modeling the slot. If a product is successfully removed from the slot, it is returned, otherwise null is returned.

toString()

The toString() method returns a String exactly like the one below for a slot with 10 M&M products. Items should start with the front slot and end with the rear slot.

SlotCount: 10 of
Product: M&Ms Cost: 1.02 Price: 1.25.
Product: M&Ms Cost: 1.02 Price: 1.25.
Product: M&Ms Cost: 1.02 Price: 1.25.
Product: M&Ms Cost: 1.02 Price: 1.25.
Product: M&Ms Cost: 1.02 Price: 1.25.
Product: M&Ms Cost: 1.02 Price: 1.25.
Product: M&Ms Cost: 1.02 Price: 1.25.
Product: M&Ms Cost: 1.02 Price: 1.25.
Product: M&Ms Cost: 1.02 Price: 1.25.
Product: M&Ms Cost: 1.02 Price: 1.25.

Resources

1. ChangeMakingMachineTest.java
2. DrinkMachineTest.java
3. SimulatorTest.java
4. SnackMachineTest.java
5. TestingConstants.java
6. VendingMachineTest.java

Part 3 - Create VendingMachine.java and test it.

The VendingMachine class is a simple vending machine. Exact change is required so it is assumed if someone is buying something they have inserted the right amount of money or have used a debit card. The get methods return the appropriate instance variable values.

Data

• DEFAULT_SIZE: int = 15 – the default size for a VendingMachine, used primarily by the default constructor
• totalProfit: int – this models the total profit for all of the VendingMachines together. It is the sum of the price of every product bought from all of the machines minus the sum of the cost of all the products ever put in all of the machines. Note that it is protected in the UML diagram so it is accessible to classes that inherit from this class.
• machineProfit: int – this models the long term profit for this particular machine. It is the sum of the price of every product bought from this machine minus the sum of the cost of all the products ever put in this machine. Note that it is protected in the UML diagram so it is accessible to classes that inherit from this class.
• slots: Slot[] – this array models the array of slots in the VendingMachine.

VendingMachine()

The default constructor creates a VendingMachine with DEFAULT_SIZE empty Slots.

VendingMachine(int size)

Creates a VendingMachine with the indicated number of empty Slots.

VendingMachine(int size, Product product)

Creates a VendingMachine with size Slots each full of product.

load()

Loads an empty or partially empty VendingMachine with a Generic product (i.e. the product obtained using the default constructor of the Product class.) Makes appropriate adjustments to machineProfit and totalProfit by subtracting costs from profit values.

load(int slotNum, int count, Product product)throws IllegalArgumentException

Loads the slot indicated by slotNum with product until it is full or until count is reached. Makes appropriate adjustments to machineProfit and totalProfit by subtracting costs from profit values. Throws an IllegalArgumentException if the slotNum is out of bounds, the count is less than or equal to zero, or if the product is null.

nextProduct(int slotNum)throws IllegalArgumentException

Returns a reference to the next available product in the indicated slot or null if the slot is empty. Throws an IllegalArgumentException if the slotNum is out of bounds.

buy(int slotNum)throws IllegalArgumentException

Models buying one item from the slot number indicated. Makes appropriate adjustments to machineProfit and totalProfit by adding the price to the profit values. Throws an IllegalArgumentException if the slotNum is out of bounds. Returns false if there is no product to buy.

resetTotalProfit()

This method resets the totalProfit static instance variable to zero. This is useful when testing to make sure that different method tests start out in a known state for the static variable so the final value can be computed without knowing the order of the test runs.

toString()

Returns a String representing the VendingMachine, each slot, the machineProfit and totalProfit exactly as shown below for a 2-slot VendingMachine filled with Generic product where nothing has been bought (so the profits are negative).

Vending Machine
SlotCount: 10 of
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
SlotCount: 10 of
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Product: Generic Cost: 0.25 Price: 0.50.
Total Profit: -5.00 Machine Profit: -5.00.

Part 4 - Create DrinkMachine.java and test it.

The drink machine inherits from the general VendingMachine described above. The only additions are a constant for the cooling charge and a different buy method which will affect the profit for the machine and the total profit differently than in the general VendingMachine. DrinkMachines will assess a charge for keeping the drink cold when the drink is purchased. This charge impacts the cost of the product to the vending machine company. It does not impact the price for the customer.

Data

• COOLING_CHARGE: int = 10 – this models the ten-cent charge assessed to each drink when it is purchased to account for the refrigeration costs of the drink machine.

DrinkMachine()

Performs the same action for the DrinkMachine as VendingMachine().

DrinkMachine(int size, Product product)

Performs the same action for the DrinkMachine as VendingMachine(int size, Product product).

buy(int slotNum) throws IllegalArgumentException

Models buying one item from the slot number indicated. Throws an IllegalArgumentException if the slotNum is out-of-bounds. Makes appropriate adjustments to machineProfit and totalProfit by adding the price

Part 5 - Create ChangeMakingMachine.java and test it.

The change-making machine will add the functionality of being able to pay with cash and potentially get change back. The change will just be returned as an integer value in cents, but the amount paid in will be determined by the number of quarters and dollars that are entered.

ChangeMakingMachine()

Performs the same action for the ChangeMakingMachine as VendingMachine()

ChangeMakingMachine(int size)

Performs the same action for the ChangeMakingMachine as VendingMachine(int size).

ChangeMakingMachine(int size, Product product)

Performs the same action for the ChangeMakingMachine as VendingMachine(int size, Product product)

buy(int slotNum, int quarters, int dollars)throws IllegalArgumentException

Models buying one item from the slot number indicated. Throws an IllegalArgumentException if the slotNum is out of bounds or if quarters or dollars are negative. Computes the amount of money put into the machine in quarters and dollars, returning -1 if there is not enough money to buy the product and returning the positive difference or “change” if there is any. Makes appropriate adjustments to machineProfit and totalProfit by adding the price to the profit values if the buy is successful.

Part 6 - Create SnackMachine.java and test it.

The snack machine will inherit from the ChangeMakingMachine. The difference is it will have an additional instance variable of an array list of products which will indicate the type of product each slot should contain and it’s load method will fill each slot completely with the particular product the slot contains, making appropriate adjustments to the profit tallies.

Data

• productList: ArrayList – contains the list of products for each slot in the SnackMachine. The first position in the productList corresponds to the product in the first slot in the slots array.

SnackMachine(ArrayList pList)

This constructor initializes the productList of the SnackMachine and creates a new snack machine where each slot is full of the product indicated in the matching position in the productList. The size of the snack machine is just the length of the productList.

load()

This load method completely fills each slot in the snack machine with the appropriate product. As a slot is filled, the total cost of the items is subtracted from the profit tallies.

Part 7 - Create Simulator.java and test it.

The simulator will provide a means of simulating a small business of vending machines. The vending machines of the business are stored in an array list. Vending machines can be added to the list using the provided method to simulate the growth of a business. Simulation of the business “running” and selling product is done by simulating a specific number of products being bought from every slot of every vending machine in the business and returning the totalProfit of all of the vending machines in cents.

Data

• vmList: ArrayList – models the list of vending machines owned by the company

Simulator(ArrayList vmList)

Instantiates a Simulator

addVM(VendingMachine vm)

Adds the VendingMachine indicated by vm to the end of the list of vending machines owned by the company.

simulate(int pCount)

Simulates buying pCount products from every slot of every VendingMachine owned by the company. Returns the totalProfit of all of the VendingMachines.

Submission

Submission for this assignment is divided into two parts that should be completed in order.

1. PA3-A (10%): Readiness Quiz
   • In order to complete Part A you should first carefully read the project specification. Once you feel confident that you have a good grasp of the project requirements, log into Canvas and complete the Part A quiz. YOU MUST ANSWER ALL QUESTIONS CORRECTLY TO GET ANY CREDIT FOR THIS PART. You may take the quiz as many times as necessary.
2. PA3-B (25%): For this part you must submit your Product.java, ProductTest.java, Slot.java, and SlotTest.java to Gradescope. Your test classes should provide 100% branch coverage for the classes they test. For this part you will have unlimited submissions.
3. PA3-C (65%): For this part you must submit .java files for all of the classes, Product.java, Slot.java, VendingMachine.java, DrinkMachine.java, ChangeMakingMachine.java, SnackMachine.java, and Simulator.java files to Gradescope. Note that you will need to use the test classes provided under Resources above to test your code before submitting to Gradescope. There will be a deduction of 1%/ea for every submissions beyond ten.

Code submitted for Parts B and C must conform to the course style guide.

Submission Penalties

Part C will include a penalty for excessive Gradescope submissions. You are allowed ten submissions with no penalty. There will be a deduction of 1%/ea for every submissions beyond ten.

Recommended Process

1. Follow the order of the parts as outlined above.
2. Develop incrementally, testing as you go.
   • As you build up to Test-Driven Development, you should supplement your efforts with at least a main method (either in one of the classes you’re already writing or perhaps better in a separate “driver class”). Since Part 1 says to create the Product class, your driver class should have something that tests whether this is working:

   • // you must know by know that you're not going to get me to write the main method for you
     // especially when eclipse is so eager to help
     Product p = new Product("Coke", 75);
     Product q = new Product();
     System.out.println(p.getName()); // aside from this being a nice thing to print
     System.out.println(p.getPrice());// these lines might also make good places
     System.out.println(q.getName()); // to put breakpoints so that you can use the debugger inspect
     System.out.println(q.getPrice());// the Product objects created by your constructors